The present invention relates to a sensor for detecting radio-frequency oscillations of the voltage in a line, with the sensor having a capacitor whose first connection can be connected to the line. A sensor such as this is used for detecting radio-frequency voltage oscillations in power stations.
Discharges and flash-overs can occur for various reasons in power stations. These lead to radio-frequency pulses, which are transmitted to one or more lines. In order to protect a power supply with high quality, these pulses must be detected and evaluated.
Sensors for detecting such oscillations are known, which have a capacitor whose first connection can be connected to the line. One or more resistors are associated with the second connection of this capacitor. The voltage drop across the resistor or resistors is measured, and is used to detect the radio-frequency oscillations. The known sensors have the disadvantage that a number of separate components are required. The space requirement for fitting these components is comparatively high. In addition, assembly is costly.
One object of the present invention is thus to provide a sensor which has fewer components, requires less space, and is easier to install.
According to the invention, this object is achieved for a sensor of the type mentioned initially in that a second connection of the capacitor is associated with a current transformer and a bush for outputting a measured signal.
The sensor according to the invention is smaller than the known sensors. It can be produced as a compact unit, and can thus easily be installed. In particular, there is no longer any need to install separate components successively, so that the installation process is considerably simplified and speeded up.
The second connection is advantageously also associated with a spark gap, which is connected in parallel with the current transformer. When unacceptably high loads occur, a short circuit occurs in the spark gap, and the current transformer is protected against being overloaded.
In one advantageous development, the second connection of the capacitor is grounded via the current transformer and the spark gap. The oscillations recorded by the capacitor are dissipated through the ground path, and only the measured signal is emitted.
According to one advantageous refinement, the sensor has an elastically mounted element for pressing against the line, and this element is connected to the first connection of the capacitor. The elastic mounting compensates for any manufacturing or installation tolerances.
According to one advantageous development, the element is spherical and is loaded by a compression spring. The use of a spherical element results in a defined contact area being provided between the element and the line. The compression spring that is used for contact pressure can be produced and installed easily, so that the production and installation costs are reduced.
The position of the element can advantageously be adjusted with respect to the sensor, in particular in the longitudinal direction of the sensor.
In consequence, the contact separation between the element and the line is adjustable, for matching to the respective application. In particular, a single sensor can be used for a number of different applications.
The invention furthermore relates to an arrangement of a sensor, in particular of a sensor as described above, on a line for detecting radio-frequency oscillations of the voltage, with the line being surrounded by a shield. According to the invention, the sensor is arranged in an intermediate space between the line and the shield. This arrangement requires only a small amount of space, is simple to install, and can be retrofitted to existing systems.
The sensor is advantageously attached to the shield. No additional components are required, so that the design and installation are simplified, and the cost is reduced.
In one advantageous refinement, the sensor has a bush for outputting a measured signal, and this bush is arranged outside the shield. Cables for tapping off the measured signal can be connected to the bush quickly and easily, and can be laid outside the shield.
According to one advantageous development, the sensor is arranged on a connecting plate which can be attached to the shield. The sensor can be installed on the connecting plate in advance, and the connecting plate is then attached to the shield. This speeds up the installation process.
The shield is advantageously provided with an insert for attachment of the sensor. This insert can be retrofitted to existing shields, so that the sensor according to the invention and the arrangement according to the invention can also be installed retrospectively in already existing systems.
According to one advantageous refinement, the shield is grounded. No special safety measures are then necessary in order to prevent contact with the shield. Furthermore, the grounding of the capacitor which is provided according to the invention can be produced via the shield. There is no need for any separate grounding cables.
Advantageous refinements and developments of the invention are described in the dependent claims.